Texts displayed for reading by means of currently available techniques are “flat” texts. In other words, any alteration in the text involves deleting a letter, word, sentence or paragraph and replacing them with a different letter, word, sentence or paragraph, or adding text and integrating it into the basic text. As a result, the display or printing of the result constitutes effectively, a new text. The displayed or printed result does not preserve or reflect the change and development of the basic text.
In many application is, it is desired to reflect information expressed in several dimensions, e.g. the text that is relevant to specific date or period. Typical example being the law text. The Law undergoes revisions from time to time, and an advocate involved in a lawsuit that refers to events that had occurred at a given period in the past should, preferably, have a convenient means for reviewing the language of the law and regulations that were relevant to the specific dates under consideration. The advocate is not interested in later revisions. In other words, the user or advocate would like to have a convenient means for displaying a given “layer” of the text which is of interest.
As will be explained in greater detail below, whilst the example above illustrated selection of layer of interest according to time dimension, (i.e. displaying a layer of text which is valid for a given time), other dimensions may be of interest either separately or in combination, e.g. displaying in parliament records, only the text layer that relates to a given spokesperson.
There is, accordingly, a need in the art for providing a convenient means for introducing and displaying layers of text according to selected dimension or dimensions.
Glossary:
There follows a glossary of terms that are used in the specification, some of which are conventional and others have been coined.
Dimension—A variable applied to a text segment, which includes information on one related level. The dimensions are not limited in definition, quantity or number of assigned values per text segment. An unlimited number of dimensions and values can be defined, meaning that the dimension will serve a great number of terms. The dimensions do not have to be defined for every text segment. A text segment that has no defined dimension will be a non-dimensional text segment.
There follows typical, yet not exclusive, types of dimensions:                A. Dimension of time—the variable that defines the validity in time of a given text segment.        B. 25 Dimension of place—the variable that defines the place where the text was created, occurred, is relevant to, etc.        C. Spokesperson dimension—the variable that defines the text of a given spokesperson.        D. Reference Dimension: a variable that defines the source of text and serves as reference to the text segment under question. Thus, for example, when a given text segment in a patent document originates from a given scientific publication (e.g. a publication from the IEEE gazette), the reference dimension that is applied to the text segment in the patent is assigned with the value of the specified scientific publication.        
Those versed in the art will readily appreciate that the dimension is by no means bound by the latter examples and, in fact, dimension may refer to any desired domain of subject. Thus, by way of non-limiting example, in a play script, a dimension may refer to passages with, say, tragic (first value) or comic (second value) connotations.
As will be explained in greater detail below, different dimensions may refer to the same text segment.
It should be noted that the dimension and value thereof do not necessarily form an integral part of the text. Thus, for example, the text segment, “inner-city fare is 200 shekels”, may be assigned with the value, “Tel Aviv” of the place dimension, without that value being part of the text segment.
A text segment may vary from the smallest unit (i.e. word), to any defined text portion (e.g. sentence, a few words, paragraph, etc). It should be noted that a text segment is not confined to any particular linguistic syntax structure.    2. Dimension Value—A quantitative value in the definition range that a dimension receives for a text segment, or in other words, the value of a given text.    3. Range of Values—The range of values that a dimension may receive. This is of particular relevance to text retrieved.    4. Status of the dimension value—The status of the given value is either valid or invalid. Put differently, for various types of dimensions, there need not necessarily be a valid value.    5. Text segment—The text portion to which a dimension variable is assigned.    16. Text—Information that is saved in a given format, and is constructed of text segments.    7. Word—A chain of characters separated by dividers on both sides (valid dividers, punctuation marks or a space).    8. Type of value continuity—Defines the behavior of values in the dimension. The permitted types of continuity are as follows:            First type: There may and must only be one valid value that is assigned to a given dimension. The beginning time (say date) of the unit of a new value will cause the former value to close on the specified date minus 1. Time dimension is an example of a first type, seeing that applying an opening date to a segment necessarily entails that the previous text segment expired one day before. Of course, the time dimension is not bound to date and may refer to a different time unit say second, minute, decade etc.        Second type: There are various dimensions that may have either valid or invalid values.        
Practically speaking, there are various functions that may be applied when editing a text so as to constitute a multi-layer text, including:                Insert—A function used to insert a text segment into a certain place in the text. This requires to assign dimensions and values to the newly inserted text segment.        End—End actually corresponds to “deletion” of text. The text is not actually deleted, but rather the dimension thereof is rendered invalid.        Author Correction—Enables to correct text (e.g. editorial errors) without affecting the dimension. In other words, the same value of a given dimension applies to the text before and after Author corrections were effected.        
Those versed in the art will readily appreciate that the specified functions may be modified and/or others may be added, all as required an appropriate.